System and method for signaling control information in a mobile communication network

ABSTRACT

A method of decoding encoded information communicated over a radio channel includes receiving a vector of encoded information transmitted by a wireless terminal. The encoded information includes an encoded representation of unencoded information bits that have been encoded using a first order Reed-Muller code. The method also includes generating a vector of transform values by performing a Hadamard Transform on the received vector and identifying a subset of the transform values based on scheduling information associated with the wireless terminal. Additionally, the method includes selecting, from the subset of transform values, one of the transform values based on a magnitude of the selected transform value and determining an estimate of the unencoded information bits based on a bit sequence associated with the selected transform value. In accordance with another embodiment of the present disclosure, an apparatus is operable to implement this method

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/077,435, filed on Mar. 31, 2011, which claims the benefit of U.S.Provisional Application No. 61/320,167, filed Apr. 1, 2010, entitled“TPC Command Transmission in Carrier Aggregation,” and U.S. ProvisionalApplication No. 61/322,190, filed Apr. 8, 2010, entitled “EfficientDecoding Methods and Apparatus for Block Coded Messages with Know Subsetof Bit Values,” both of which are incorporated by reference in theirentirety.

TECHNICAL FIELD OF THE INVENTION

This disclosure relates in general to wireless communication and, moreparticularly, to managing the transmission power of a mobile terminal.

BACKGROUND OF THE INVENTION

Modern mobile communication networks face an ever increasing demand forhigh-bandwidth communication services under a wide variety of radioconditions. Some communication technologies have responded to this needby utilizing an expanded radiofrequency spectrum. For example, Release 8of the 3GPP Long Term Evolution (LTE) standard utilized a 20-MHzbandwidth for carrier signals, but Release 10 is expected to utilize aspectrum of 100-MHz or more.

Because backwards compatibility is often a requirement for mobilecommunication networks, networks supporting use of expanded spectrumsare often required to support legacy devices incapable of recognizing orutilizing their larger bandwidth. The need to support terminals having arange of different capabilities creates significant difficulties inmanaging resource use in such networks. To facilitate use of expandedcarrier spectrums while still maintaining backwards compatibility,certain communication technologies, such as LTE, utilize a “carrieraggregation” scheme. Under such a scheme, a legacy terminal that isincapable of using the entirety of the expanded carrier spectrum willrecognize the expanded spectrum as multiple separate carrier spectrums,referred to as “Component Carriers” (CCs) that are each sized to fit thecapabilities of the legacy terminal. Meanwhile current-generationterminals will be able to utilize a larger carrier spectrum byaggregating multiple CCs.

However, use of multiple separate carrier spectrums can significantlycomplicate configuration and management of networks. For example, if thenetwork attempts to notify a mobile device over a non-ideal radiochannel that the device has been scheduled to use a particular componentcarrier, the mobile device may not successfully receive thenotification. Even though many modern communication technologies provideprocedures for a device to request retransmission of information thatwas not successfully received, it may be difficult or impossible for adevice to determine that it has not received scheduling information ifthe device is uncertain what scheduling information to expect.Furthermore, while the device could simply report on all the schedulinginformation it receives, and thereby permit the network to determine bydeduction what scheduling information the device did not receive, asignificant amount of the network's transmission resource would be usedup unnecessarily on such signaling when the mobile device successfullyreceives all the scheduling information. Thus, finding an effectivescheme for communicating information about the scheduling of componentcarriers—one that can accommodate and adapt to transmission errors—canbe critical to performance in networks that support carrier aggregation.

SUMMARY OF THE INVENTION

In accordance with the present disclosure, certain disadvantages andproblems associated with mobile communication have been substantiallyreduced or eliminated. In particular, certain devices and techniques forproviding mobile telecommunication service are described.

In accordance with one embodiment of the present disclosure, a method ofdecoding encoded information communicated over a radio channel includesreceiving a vector of encoded information transmitted by a wirelessterminal. The encoded information includes an encoded representation ofunencoded information bits that have been encoded using a first orderReed-Muller code. The method also includes generating a vector oftransform values by performing a Hadamard Transform on the receivedvector and identifying a subset of the transform values based onscheduling information associated with the wireless terminal.Additionally, the method includes selecting, from the subset oftransform values, one of the transform values based on a magnitude ofthe selected transform value and determining an estimate of theunencoded information bits based on a bit sequence associated with theselected transform value. In accordance with another embodiment of thepresent disclosure, an apparatus is operable to implement this method.

In accordance with another embodiment of the present disclosure, amethod of decoding encoded information communicated over a radio channelincludes receiving a vector of encoded information transmitted by awireless terminal. The encoded information includes an encodedrepresentation of unencoded information bits that have been encoded by asecond order Reed-Muller code. The method also includes determining aplurality of hypothesized sequences corresponding to a first group ofthe unencoded information bits. Each hypothesized sequence includes anestimate for each of the first group of unencoded information bits.Additionally, the method includes, for each hypothesized sequence,multiplying the received vector by a covering vector associated with therespective hypothesized sequence to obtain a modified received vectorand, for each modified received vector, generating a vector of transformvalues by performing a Hadamard Transform on the modified receivedvector. Each of the transform values is associated with one or moreestimates of a second group of the unencoded information bits. Themethod also includes identifying a subset of the transform values basedon the scheduling information associated with the wireless terminal andselecting, from the identified subset of transform values, one of thetransform values based on a magnitude of the selected transform value.The method also includes determining an estimate of the unencodedinformation bits. This estimate includes an estimate of the first groupof unencoded information bits based on the hypothesized sequenceassociated with the modified vector used to generate the selectedtransform value and an estimate of the second group of unencodedinformation bits associated with the selected transform value. Inaccordance with another embodiment of the present disclosure, anapparatus is operable to implement this method.

Important technical advantages of certain embodiments of the presentinvention include reducing the required overhead for control signalingin systems supporting carrier aggregation. Particular embodiments may becapable of limiting the control signaling overhead associated withcarrier aggregation when a terminal is not utilizing multiple componentcarriers. Additionally, particular embodiments may be able to providethis overhead reduction using a robust signaling scheme that can adaptto transmission errors that may impair the relevant signaling. Otheradvantages of the present invention will be readily apparent to oneskilled in the art from the following figures, descriptions, and claims.Moreover, while specific advantages have been enumerated above, variousembodiments may include all, some, or none of the enumerated advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsadvantages, reference is now made to the following description, taken inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates the carrier spectrum for an example communicationsystem that utilizes carrier aggregation;

FIG. 2 illustrates a particular embodiment of a mobile communicationsystem that supports carrier aggregation;

FIGS. 3A-3D are tables providing example power control parameters thatmay be utilized in particular embodiments of the mobile communicationsystem of FIG. 2;

FIG. 4 is a table of covering vectors that may be utilized to decodeinformation in particular embodiments of the mobile communicationsystem;

FIG. 5 is a table showing a comparison of the operational complexity ofvarious decoding techniques that can be used to decode encoded feedbackinformation;

FIG. 6 is a block diagram illustrating a particular embodiment of awireless terminal that may be supported by the mobile communicationsystem;

FIG. 7 is a flowchart showing example operation of a particularembodiment of the wireless terminal in selecting a format for uplinkcontrol messages;

FIG. 8 is a flowchart showing example operation of a particularembodiment of the wireless terminal in determining a transmission powerlevel at which to transmit uplink control messages;

FIG. 9 is a block diagram illustrating a particular embodiment of anetwork node that may be utilized in mobile communication system;

FIG. 10 is a flowchart showing example operation of the network node inmanaging the transmission power level of the wireless terminal; and

FIGS. 11-12 are flowcharts illustrating example operation of particularembodiments of the network node in decoding feedback informationtransmitted by the wireless terminal.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates the carrier spectrum for an example communicationsystem that utilizes carrier aggregation. Certain advanced communicationtechnologies rely on carrier aggregation to facilitate use of anexpanded carrier spectrum 110 in networks that must also support legacyterminals that are only capable of utilizing smaller carrier spectrums.Under a carrier aggregation scheme, expanded carrier spectrum 110 canappear to a legacy terminal as the aggregate spectrum for multiplecarriers 100 (referred to as “component carriers” (CCs)), each having asmaller spectrum that is compatible with the capabilities of the legacyterminal. Current-generation terminals, however, can utilize a largerportion of the expanded spectrum 110 by transmitting or receiving overmultiple of the component carriers 100.

As one example, Release 8 of the Long Term Evolution (LTE) communicationstandard supports a carrier spectrum having bandwidths up to 20 MHz. Asa result, terminals configured to support this standard may be limitedto using carriers having a bandwidth no greater than 20 MHz. However, inorder to provide higher overall throughput, Release 10 of LTE isexpected to support a carrier spectrum having a bandwidth larger than 20MHz. As a result, future releases of LTE will use carrier aggregation toprovide spectrum compatibility. With carrier aggregation, this overallspectrum will appear to a Release 8 terminal as the aggregate spectrumof multiple component carriers, each having a smaller spectrum (e.g., 20MHz) compatible with the capabilities of the Release 8 terminal.Meanwhile, a Release 10 terminal may be able to utilizing the entiretyof this expanded carrier spectrum 110 by utilizing multiple componentcarriers 100 simultaneously. While the description below focuses, forpurposes of illustration, on implementing the described solutions in LTEnetworks, the described solutions may be implemented, with appropriatemodification, to any suitable communication technologies.

FIG. 2 illustrates a mobile communication system 10 that providescommunication service to a wireless terminal 20 using a carrieraggregation scheme, such as the one illustrated in FIG. 1. Mobilecommunication system 10 includes an access network 30 that providescommunication services to a cell 60 associated with mobile communicationsystem 10 and a core network 40 that provides backhaul delivery ofinformation within mobile communication system 10. By using signalingtechniques described herein, particular embodiments of mobilecommunication system 10 can provide a reliable scheme for communicatingscheduling information and power settings between access network 30 andwireless terminal 20 regardless of the number of components carriersconfigured for wireless terminal 20. Additionally, by using knowledge ofthe component carriers on which wireless terminal 20 has been scheduled,access network 30 can more efficiently decode feedback transmitted bywireless terminal 20 indicating the scheduled transmissions successfullyreceived by wireless terminal 20. Consequently, as described furtherbelow, particular embodiments of mobile communication system 10 canprovide robust, low-overhead techniques for managing the use of carrieraggregation.

In general, mobile communication system 10 provides mobile communicationservice to one or more wireless terminals 20 operating within cell 60, ageographic area associated with mobile communication system 10. Mobilecommunication system 10 may support communication of any suitable typeand/or in accordance with any appropriate communication standardsincluding, but not limited to, any Long Term Evolution (LTE), WorldwideInteroperability for Microwave Access (WiMAX), and Wideband CodeDivision Multiple Access (WCDMA) communication standards.

Wireless terminal 20 represents any device capable of communicatinginformation wirelessly with mobile communication system 10. Examples ofwireless terminal 20 include traditional communication devices such asmobile phones, personal digital assistants (“PDAs”), laptop computers,and any other portable communication device suitable for use withcommunication system 10. For example, in particular embodiments,wireless terminal 20 represents an instance of LTE user equipment (UE).Additionally, in particular embodiments, wireless terminal 20 may alsorepresent automated equipment or devices equipped with componentssuitable to permit communication with mobile communication system 10,such as devices in a home-automation network. For example, wirelessterminal 20 may represent a washing machine, oven, digital videorecorder (DVRs), or other home appliances capable of remote managementover mobile communication system 10. Although FIG. 2 illustrates, forthe sake of simplicity, only a single wireless terminal 20 and a singlebase station 32, mobile communication system 10 may include any suitablenumber and configuration of base stations 32 capable of serving anynumber of wireless terminals 20 including, in particular embodiments,wireless terminals 20 having different capabilities with respect to thecarrier spectrums they support.

Access network 30 communicates wirelessly with wireless terminals 20 andserves as an interface between wireless terminals 20 and core network40. Access network 30 may represent or include a radio access networkand/or any elements responsible for providing a radio or air interfacefor core network 40. For example, in the illustrated embodiment, accessnetwork 30 includes one or more base stations 32. Access network 30 mayalso include base station controllers, access servers, gateways, and/orany additional components suitable for managing radio channels used bybase station 32, authenticating users, controlling handoffs between basestation 32 and other radio access elements, and/or otherwise managingthe interoperation of base stations 32 and interfacing base stations 32with core network 40.

Base station 32 communicates wirelessly with wireless terminals 20 tofacilitate mobile communication for wireless terminals 20. Base stations32 may include any appropriate elements to communicate with wirelessterminals 20 and to interface wireless terminals 20 with core network40. For example, depending on the communications standards supported byaccess network 30 and core network 40, each base station 32 mayrepresent or include a base station, a Node B, an evolved Node B (eNodeB), a radio base station (RBS), an access point, or any other suitableelement capable of communicating with wireless terminals 20 wirelessly.

Core network 40 routes voice and/or data communicated by wirelessterminals 20 from access network 30 to other wireless terminals 20 or toother communication devices coupled to core network 40 through landlineconnections or through other networks. Core network 40 may support anyappropriate standards or techniques for routing such communications. Forexample, in embodiments of wireless terminals 20 that support LTE, corenetwork 40 may represent a System Architecture Evolution (SAE) corenetwork. Core network 40 may also be responsible for aggregatingcommunication for longhaul transmission, authenticating users,controlling calls, metering usage for billing purposes, or otherfunctionality associated with providing communication services. Ingeneral, however, core network 40 may include any components suitablefor routing and otherwise supporting voice and/or data communicationsfor wireless terminals 20.

In operation, mobile communication system 10 provides telecommunicationservice to wireless terminal 20. As part of this service, access network30 communicates wirelessly with wireless terminal 20. For example, inthe illustrated embodiment, base station 32 of access network 30establishes a wireless connection with wireless terminal 20 forcommunication over radiofrequency (RF) channels, and core network 40transports voice, data, multimedia, and/or other types of informationbetween various components of access network 30 and between otherelements of mobile communication system 10, such as wirelinecommunication devices.

To increase the available spectrum of carriers that can be utilized forcommunication between wireless terminal 20 and access network 30, mobilecommunication system 10 utilizes a carrier aggregation scheme in whichone or more component carriers are configured for use in cell 60. Inparticular embodiments, this configuration is performed on a semi-staticbasis. The number of configured component carriers, as well as thebandwidth of the individual component carriers, may be different foruplink and downlink. Additionally, the number of component carriersconfigured in a cell may be different from the number of componentcarriers seen by wireless terminal 20. For example, in particularembodiments, wireless terminal 20 may support more downlink componentcarriers than uplink component carriers, even though cell 60 isconfigured with the same number of uplink and downlink componentcarriers. In particular embodiments, wireless terminal 20 may initiallyconnect to access network 30 through base station 32 using only a singlecomponent carriers, and after connecting, may be provided informationindicating the component carriers currently configured for use in cell60

In order to prevent wireless terminal 20 from having to constantlymonitor all component carriers configured for cell 60, an element ofaccess network 30 (assumed to be base station 32 for purposes of thisexample) may be responsible for activating and deactivating the variouscomponent carriers to be used by wireless terminal 20 in cell 60.Wireless terminal 20 can then limit its monitoring to only thosecomponent carriers configured and activated for wireless terminal 20.For example, in Release 10 LTE embodiments, important controlinformation for a component carrier will be transmitted on a PhysicalDownlink Control CHannel (PDCCH) and Physical Downlink Shared CHannel(PDSCH) associated with that component carrier. With activation,wireless terminal 20 can limit its monitoring of PDCCH and PDSCH tocomponent carriers currently activated for wireless terminal 20, insteadof being forced to monitor these channels for all component carriersconfigured for use in cell 60. In certain embodiments, activation can beachieved using faster signaling (e.g., Medium Access Control (MAC) layersignaling) than the initial configuration of component carriers, therebyreducing the amount of time and overhead used to change the number ofcomponent carriers utilized by wireless terminal 20 at a given time. Forexample, upon arrival of large data amounts for wireless terminal 20multiple downlink component carriers may be activated for wirelessterminal 20 and then used to transmit data to wireless terminal 20.These excess component carriers may then be de-activated for wirelessterminal 20 if not needed once this data has been transmitted towireless terminal 20.

In particular embodiments, all but one component carrier in eachdirection—referred to here, individually, as the “downlink primarycomponent carrier” and the “uplink primary component carrier,” orcollectively, as the “primary component carrier”—can be de-activated forwireless terminal 20 when not needed. Activation provides therefore thepossibility to configure multiple component carriers for wirelessterminal 20, but only activate these additional componentcarriers—referred to here as “secondary component carriers”—on anas-needed basis. Often, wireless terminal 20 may have one or a very fewcomponent carriers activated, thereby permitting wireless terminal 20 touse a lower reception bandwidth and thus reduce battery consumption.

In many advanced communication systems, scheduling of component carriersis done via downlink assignments, uplink scheduling grants, and/or otherscheduling information that is communicated in messages (represented inFIG. 2 by “downlink control messages 70”) sent to wireless terminal 20over a downlink control channel. For example, in an embodiment of mobilecommunication system 10 implementing LTE, downlink assignments would becommunicated to wireless terminal 20 in Downlink Control Information(DCI) messages transmitted on the PDCCH. This scheduling informationindicates that wireless terminal 20 has been scheduled to receive adownlink transmission on a particular component carrier during aparticular radio subframe. For example, in embodiments of mobilecommunication system 10 that implement LTE, base station 32 may transmita downlink control message 70 that includes one or more downlinkscheduling assignments indicating when in the current or upcomingsubframe wireless terminal 20 is scheduled to receive a datatransmission on the Physical Downlink Shared CHannel (PDSCH) on aparticular component carrier or carriers.

Wireless terminal 20 determines the component carrier associated withreceived scheduling information either based on a predeterminedrelationship between the component carrier on which the schedulinginformation was received (e.g., the relevant component carrier may bethe same component carrier on which the scheduling information wasreceived for a downlink assignment or an uplink component carrierassociated with that downlink component carrier for uplink schedulinggrants) or based on additional information included in the downlinkcontrol message 70 that identifies the relevant component carrier (suchas a Carrier Indicator Field (CIF) in LTE embodiments). In particularembodiments, the applicable subframe for the scheduling information isthe same subframe in which the downlink control message 70 istransmitted, or another subframe identified by wireless terminal 20based on some pre-established relationship with the subframe in whichdownlink control message 70 was transmitted.

In addition to the scheduling information, downlink control messages 70may contain, in particular embodiments, modulation and coding schemeparameters, spatial multiplexing parameters, and feedback-relatedinformation. Additionally, in particular embodiments, control messagesmay include power control parameters (e.g., Transmit Power Control (TPC)commands), as discussed further below. These parameters provideinformation indicating how wireless terminal 20 should respond to thedownlink control message 70 or how wireless terminal 20 should behavewhen using the scheduled resource.

In many advanced communication technologies, wireless terminal 20 isexpected to respond to a downlink control message 70 by indicatingwhether the data transmission(s) scheduled by the relevant downlinkcontrol message 70 were successfully received (including both receptionand decoding of the relevant transmissions without error). Thus, inparticular embodiments, wireless terminal 20 responds to a detecteddownlink control message 70 by communicating an uplink control message72 that includes feedback information (e.g., Hybrid Automatic RepeatRequest (HARQ) Acknowledgement/Negative Acknowledgement (ACK/NACK)feedback bits) indicating successful receipt or unsuccessfulreceipt/non-receipt of the transmission(s) scheduled by that downlinkcontrol message 70. However, when carrier aggregation is implemented ina network, particularly one supporting legacy terminals unable toutilize multiple component carriers, the configuration and communicationof uplink control messages 72 can become far more complicated.Communication of feedback for a significant number of differentcomponent carriers can waste value transmission resources. Additionally,the dramatic increase in the number of possible configuration andscheduling scenarios can create problems if the communication of thisinformation is not robust. Therefore, particular embodiments of mobilecommunication system 10 implement certain solutions for improvedcommunication of control signaling in carrier aggregation systems.

In particular embodiments, wireless terminal 20 is configured by thenetwork to make scheduling requests (SR) with a pre-determinedfrequency. When a wireless terminal 20 is to feed back bits in asubframe that allows scheduling request, the SR bit (where, e.g., “1”may represent a positive scheduling request and “0” may represent anegative scheduling request) can be appended to the feedback bitsequences. Thus, uplink control message 72 may also include an SR bit oran other form of scheduling request in addition to the feedback bits.

Format Selection for Uplink Control Messages

If wireless terminal 20 has multiple component carriers activated at aparticular moment, it may be necessary for wireless terminal 20 toprovide feedback on transmissions scheduled on multiple differentcomponent carriers at once. In particular embodiments of mobilecommunication system 10, wireless terminal 20 may be configured to use asingle uplink control message 72 to acknowledge receipt ornon-receipt/failed receipt of scheduled information on all scheduledcomponent carriers during a particular subframe. By consolidating theacknowledgements in this manner, mobile communication system 10 mayreduce the overhead required for such acknowledgements. However, legacyterminals served by mobile communication system 10 may only be capableof using (and therefore acknowledging) a single component carrier. As aresult, it may be necessary for mobile communication system 10 torecognize multiple formats of uplink control message 72, including afirst format for devices capable of utilizing only a single componentcarrier, a format that only provides feedback for a single componentcarrier (referred to here as the “single carrier” or “SC” format), and asecond format that can be used to communicate feedback for multiplecomponent carriers (referred to here as the “carrier-aggregation” or“CA” format).

In particular embodiments, the second format represents a message formatthat defines, within an uplink control message 72, predeterminedlocations for one or more feedback bits associated with each of thecomponent carriers currently configured for use in cell 60. The specificnumber of bits transmitted for each component carrier may vary. Forexample, in particular embodiments, mobile communication system 10supports multiple-input multiple-output (MIMO) and spatial diversitytransmission schemes and may selectively utilize spatial feedbackbundling. In such embodiments, wireless terminal 20 may be configured touse a CA format that provides one feedback bit per configured componentcarrier when spatial feedback bundling is employed, and provides twofeedback bits per configured component carrier when spatial bundling isnot employed. For example, if cell 60 is currently configured with threecomponent carriers, this CA format would support three bits when spatialfeedback bundling is employed and six bits when spatial feedbackbundling is not employed. Unneeded feedback bits (e.g., those associatedwith a component carrier for which no scheduling information wassuccessfully received, or those associated with a single-codewordtransmission that requires only one of an allotted two feedback bits)may be set to a fixed value, e.g., “0” (NACK). In general, however, theCA format may indicate in any appropriate manner whether scheduledinformation for each of a plurality of component carriers has or has notbeen successfully received by wireless terminal 20.

Because of the additional overhead associated with using the CA format,it may be desirable to have terminals that are capable of utilizingmultiple component carriers also use the SC format for uplink controlmessages 72 if such terminals have only been scheduled on a singlecomponent carrier (and, thus, only need to provide feedback on a singlecomponent carrier). Therefore, in particular embodiments, wirelessterminal 20 transmits uplink control messages 72 in accordance with theSC format when providing feedback regarding a transmission wirelessterminal 20 is scheduled to receive on a single component carrier (e.g.,the primary component carrier) and in accordance with the CA format whenproviding feedback on transmissions wireless terminal 20 is scheduled toreceive on multiple component carriers. Consequently, particularembodiments of mobile communication system 10 may reduce the overheadassociated with control information transmissions by wireless terminals20 that support carrier aggregation.

However, because access network 30 may communicate downlink controlmessages 70 over non-ideal radiofrequency (RF) channels, downlinkcontrol messages 70 carrying assignments and scheduling grants may notbe received or may be corrupted during transmission, resulting in errorswhen decoded by wireless terminal 20. As a result, wireless terminal 20may not receive all of the downlink control messages 70 transmitted toit for a particular subframe. One particular concern is that wirelessterminal 20 may receive a downlink control message 70 with schedulinginformation for a secondary component carrier, but fail to receive thedownlink control message 70 with scheduling information for the primarycomponent carrier during the same subframe. In such cases, using the SCformat to provide feedback on the downlink control message 70 for thesecondary component carrier could lead to errors, because the SC formatuplink control message 72 only provides feedback on a single componentcarrier. Because, in this case, multiple component carriers have beenscheduled for wireless terminal 20, access network 30 may not be able toconclusively determine which of the scheduled component carriers thefeedback was associated with.

Consequently, in particular embodiments, wireless terminal 20 isconfigured to select a format for uplink control messages 72 based onwhether wireless terminal 20 receives scheduling information for anysecondary component carrier associated with cell 60. In particularembodiments, wireless terminal 20 knows which component carrier is theprimary component carrier (for example, as a result of informationtransmitted by base station 32 during configuration of the componentcarriers) or is able to determine from the format of a received downlinkcontrol messages 70 whether the corresponding component carrier is theprimary or a secondary component carrier. If wireless terminal 20successfully receives scheduling information for any secondary componentcarrier, wireless terminal 20 responds with a CA format uplink controlmessage 72, even if this secondary component carrier is the onlycomponent carrier for which wireless terminal 20 successfully receivesscheduling information for that subframe. By doing so, in particularembodiments, wireless terminal 20 is able to prevent errors that wouldotherwise result if wireless terminal 20 used the SC format to providefeedback on secondary component carriers when wireless terminal 20 hasnot successfully received scheduling information transmitted for theprimary component carrier. In such embodiments, wireless terminal 20 maystill use the SC format to transmit feedback when wireless terminal 20the only component carrier for which wireless terminal 20 receivesscheduling information is the primary component carrier, just not when asecondary component carrier is the only component carrier for whichscheduling information is received.

In general, this solution permits access network 30 to conclusivelyestablish, when receiving an uplink control message 72 with feedbackinformation for only a single component carrier (i.e., an SC formatmessage), that the feedback information relates to a scheduledtransmission on the primary component carrier. Furthermore, inparticular embodiments of mobile communication system 10, access network30 is configured to always schedule wireless terminal 20 on the primarycomponent carrier first. In such embodiments, wireless terminal 20 mayoften be scheduled on only the primary component carrier. As a result,wireless terminal 20 may still be able to use the SC format often,limiting the frequency with which the CA format, with its additionaloverhead, is used. Thus, particular embodiments of mobile communicationsystem 10 permit wireless terminal 20 to opportunistically use the SCformat to reduce the control signaling overhead associated with carrieraggregation, but at the same time avoid certain errors that may resultwhen scheduling information is unsuccessfully transmitted. FIG. 7 belowdescribes in greater detail example operation of a particular embodimentof wireless terminal 20 capable of providing feedback in this manner.

Communicating Power Control Parameters

Particular embodiments of mobile communication system 10 may also oralternatively provide a more reliable technique for controlling thetransmission power of terminals when sending uplink control messages 72associated with carrier aggregation. In particular embodiments of mobilecommunication system 10, each downlink assignment or uplink grant isscheduled with its own downlink control message 70 and each receiveduplink control message 72 contains a power control parameter thatindicates directly or indirectly a transmission power level for wirelessterminal 20 to use in transmitting the responsive uplink control message72. These power control parameters may represent information indicatinga specific transmission power level for wireless terminal 20 to use,information indicating a maximum transmission power level wirelessterminal 20 must obey, information indicating an adjustment for wirelessterminal 20 to apply to a current transmission power level, orinformation indicating in any other manner an appropriate transmissionpower level for wireless terminal 20. As one example, in certain LTEembodiments, each downlink control message 70 contains a Transmit PowerControl (TCP) bit field that contains an adjustment value for wirelessterminal 20 to apply to a current power level in determining anappropriate transmission power level at which to transmit a responsiveuplink control message 72 on the PUCCH.

As explained above, when scheduled for transmission on the primarycomponent carrier as well as one or more secondary component carriers,wireless terminal 20 will receive multiple downlink control messages 70,one for each component carrier on which the terminal is scheduled. Insuch embodiments, it would be possible to only transmit the desiredpower control parameter in one downlink control message 70 and reuse therelevant fields in other downlink control messages 70 for other,non-redundant control information.

However, doing so can create several problems. First, if the powercontrol parameter were inserted into only a single downlink controlmessage 70 transmitted to wireless terminal 20 and wireless terminal 20does not successfully receive that downlink control message 70, wirelessterminal 20 might not have sufficient information by which to determinethe correct transmission power to use in transmitting the responsiveuplink control message 72. Second, even if wireless terminal 20 were toreceive the downlink control message 70 containing the true powercontrol parameter, access network 30 would be unlikely to find a singlepower control parameter suitable for use with both the SC format and theCA format, as these two formats may result in drastically differentuplink transmissions.

Furthermore, in particular embodiments, the CA format provides feedbackfor all configured component carriers. Since re-configuration is arather slow process, the number of configured component carriers cannottrack the actually used component carriers and often a rather highnumber of component carriers is configured for a given cell 60.Therefore, it is quite likely that, for a given subframe, cell 60 willbe configured with more component carriers than wireless terminal 20will actually be scheduled to use. This may result in a yet a thirdproblem. Wireless terminal 20 may transmit feedback bits that would beunnecessary if wireless terminal 20 provided feedback for only activatedor scheduled component carriers. This in turn results in lower energyper true feedback bit and worse performance.

To address the third problem (i.e., diminished performance resultingfrom the transmission of more feedback bits than are necessary),particular embodiments of base station 32 implement a dynamic decodingscheme to decode feedback bits transmitted by wireless terminal 20 afterreceiving these downlink control messages 70. This dynamic decodingscheme utilizes scheduling knowledge to improve the base station'sdecoding performance for a given transmission power level. As a result,the dynamic decoding can provide the same quality level with asubstantial reduction in the signal-to-noise ratio, thereby reducing thenegative impact of the unnecessary feedback bits. This dynamic decodingscheme is described in greater detail below.

To address the first and second problems, an appropriate element ofaccess network 30 (assumed here to be base station 32) may be configuredto determine a power control parameter to include in each downlinkcontrol message 70 based on whether the relevant downlink controlmessage 70 is communicating scheduling information for the primarycomponent carrier, a “PCC control message” (represented in FIG. 2 bydownlink control message 70 a), or communicating scheduling informationfor one of the secondary component carriers, an “SCC control message”(represented in FIG. 2 by downlink control messages 70 b-d). Inparticular embodiments, if the relevant downlink control message 70 is aPCC downlink control message, base station 32 selects a first powercontrol parameter suitable for use in transmitting an uplink controlmessage 72 in accordance with the SC format. If, instead, the relevantdownlink control message 70 is an SCC control message, then base station32 determines a second power control parameter or multiple power controlparameters suitable for wireless terminal 20 to use in transmitting aresponsive uplink control message 72 in accordance with the CA format.

Base station 32 may determine this second and/or any additional powercontrol parameter for use with the CA format in any suitable manner. Asone example, in particular embodiments, base station 32 determines asecond power control parameter for transmitting uplink control message72 using the CA format regardless of how many or which downlink controlmessages 70 wireless terminal 20 receives. In such embodiments, basestation 32 may then include this second power control parameter in eachof SCC downlink control messages 70 b-d. This may ensure that wirelessterminal 20 will use the same transmission power regardless of how manyof the multiple SCC downlink control messages 70 b-d wireless terminal20 successfully receives.

As another example, the second power control parameter determined bybase station 32 may represent a power control parameter for use whenwireless terminal 20 successfully receives all of the SCC downlinkcontrol messages 70 transmitted to wireless terminal 20 for thatsubframe. Base station 32 may intend for wireless terminal 20 tocalculate an actual power control parameter to use based on this secondpower control parameter and on the number of SCC downlink controlmessages 70 that wireless terminal 20 successfully receives. As aresult, base station 32 may calculate a third power control parameter bydividing the second power control parameter by the number of secondarycomponent carriers on which wireless terminal 20 is being scheduled inthis subframe. Base station 32 may then include this third power controlparameter in each SCC downlink control message 70 b-d. Alternatively,base station 32 may calculate multiple, different additional powercontrol parameters—one for each SCC downlink control message 70 b-d tobe transmitted—that add up to the second power control parameter. Basestation 32 then includes one of these additional power controlparameters in each SCC downlink control message 70 b-d transmitted. Ifwireless terminal 20 then successfully receives some or all of thetransmitted SCC downlink control messages 70 b-d, wireless terminal 20will add the power control parameters in the received SCC downlinkcontrol messages 70 b-d (with carrier-specific weightings in certainembodiments) to get a power control parameter for use in making a CAformat transmission in the subframe.

As yet another example, base station 32 may determine a second and/oradditional power control parameters based on the specific set ofsecondary component carriers on which wireless terminal 20 is scheduledto receive a transmission during the subframe. To illustrate, FIGS.3A-3D provide tables containing example power control parameters for anembodiment in which base station 32 is capable of supporting fivedifferent component carriers. Specifically, the tables of FIGS. 3A-3Ddescribe example power control parameters for a particular embodiment ofbase station 32 when two, three, four, or five component carriers,respectively, are configured for wireless terminal 20. In particular,FIGS. 3A-3D illustrate example power control parameters for anembodiment in which wireless terminal 20 determines a transmission powerlevel for transmitting uplink control messages 72 in accordance withEquation 1:

P _(PUCCH)(i)=min {P _(CMAX) ,P ₀ _(_) _(PUCCH) +PL+h(n _(CQI) , n_(HARQ))+Δ_(F) _(_) _(PUCCH)(F)+g(i)}  (1)

-   for which the following definitions are used:-   P_(PUCCH) (i) PUCCH transmit power for subframe i.-   P_(CMAX) Configured maximum transmit power for uplink PCC.-   P₀ _(_) _(PUCCH) Desired uplink control message receive power    signaled by higher layers.-   h(n_(CQI), n_(HARQ)) Offset parameter that depends on number of CQI    bits or number n_(CQI) of CQI bits or number n_(H) of feedback bits-   Δ_(F) _(_) _(PUCCH) (F) Offset parameter that depends on uplink    control message format-   g(i) Accumulated power adjustment value derived from power control    parameters. δ_(PUCCH)(i). In particular embodiments,

${g(i)} = {{g(i)} + {\sum\limits_{m = 0}^{M - 1}\; {\delta_{PUCCH}\left( {i - k_{m}} \right)}}}$

The values M and k_(m) depend on whether the duplexing mode is FDD orTDD.

-   PL Pathloss

Base station 32 may store lookup tables containing the same or similarinformation to that shown in FIG. 3A-3D. Additionally, base station 32may maintain multiple different versions of each lookup table to useunder different radio conditions, with difference carrierconfigurations, or in response to changes in other aspects of theoperating environment. In such embodiments, base station 32 selects anappropriate second power control parameter using such lookup tables.Base station 32 then includes the selected second power controlparameter in each of the SCC downlink control messages 70 b-dtransmitted to wireless terminal 20. Alternatively, base station 32 may,as described above, calculate a third power control parameter and/oradditional power control parameters for inclusion in the SCC downlinkcontrol messages 70 based on the selected second power controlparameter.

As yet another example, in particular embodiments, base station 32 maydetermine the second power control parameter (or any additional powercontrol parameter to be included in SCC downlink control messages 70)based on whether spatial feedback bundling will be employed by wirelessterminal 20. For example, any of the above described techniques forgenerating additional power control parameters can be modified tofurther consider whether spatial feedback bundling will be employed.This may permit the transmission power to be adjusted based on thenumber of feedback bits that will actually be transmitted.

Base station 32 then transmits any generated downlink control messages70 to wireless terminal 20. Wireless terminal 20 successfully receives(i.e., receives and decodes without error) some or all of thetransmitted downlink control messages 70. Based on the successfullyreceived downlink control messages 70, wireless terminal 20 determines atransmission power level to use when transmitting the responsive uplinkcontrol message 72. If wireless terminal 20 successfully receives onlyPCC downlink control message 70 a, wireless terminal 20 will determine atransmission power level for transmitting a responsive uplink controlmessage 72 using the power control parameter in the only downlinkcontrol message 70 successfully received by wireless terminal 20 (inthis case, the first power control parameter). If wireless terminal 20successfully receives any of SCC downlink control messages 70 b-d, thenwireless terminal 20 will instead determine a transmission power levelto use based on power control parameters in one or all of thesuccessfully received SCC downlink control messages 70 b-d (i.e., thesecond or additional power control parameters). As explained above,wireless terminal 20 may determine the overall power control parameterto use based on a common power control parameter that is included eachof the successfully received SCC downlink control message 70 b-d, basedon the sum (possibly weighted) of the power control parameters includedin the successfully received SCC downlink control messages 70 b-d, orbased on any appropriate combination of the power control parameters inone or more of the successfully received SCC downlink control messages70 b-d.

Thus, wireless terminal 20 uses the first power control parameter (i.e.,the power control parameter included in the downlink control message 70scheduling wireless terminal to receive transmissions on the primarycomponent carrier) when base station 32 has only scheduled wirelessterminal 20 to receive transmissions on the primary component carrier,or when wireless terminal 20 does not successfully receive downlinkcontrol messages 70 communicating the scheduling of any secondarycomponent carriers. If, however, wireless terminal 20 successfullyreceives any downlink control messages 70 scheduling wireless terminal20 to receive transmissions on a secondary component carrier, thenwireless terminal 20 will disregard the first power control parameterand determine the appropriate transmission power level based on thepower control parameters in one or more of the downlink control messages70 scheduling such secondary component carriers.

After determining the power control parameter or parameters to use basedon the successfully received downlink control messages 70, wirelessterminal 20 will calculate a transmission power for its uplink controlmessage 72 based on this power control parameter. Wireless terminal 20may determine the transmission power in any appropriate manner based onthe power control parameters communicated by base station 32 in downlinkcontrol messages 70. For example, in particular embodiments, wirelessterminal 20 is configured to determine a transmission power level forthe downlink control message 70 based on Equation (1).

In particular embodiments that utilize Equation (1), g(i) is theaccumulation of the current power control parameter (or the (weighted)sum of power control parameters successfully received in downlinkcontrol messages 70 scheduling secondary component carriers) andprevious values. Depending on whether the relevant power controlparameters are used to maintain a single g(i) value or two independentg(i) values—one for the SC format (g_(PCC)(i)) and one for the CA format(g_(SCC)(i))—such embodiments may utilize separate power control loopsfor the different formats.

In the first case where only one a single g(i) value is maintained, thisg(i) is only updated with the power control parameter related to theformat to be used for the responsive uplink control message 72. Thus,whenever the SC format is used, g(i) is updated based on the powercontrol parameter transmitted in the PCC downlink control messages 70(i.e., the first power control parameter), assuming the PCC downlinkcontrol message 70 was successfully received. Whenever the CA format isused, g(i) is updated based on one or more of the power controlparameters in successfully received downlink control messages 70scheduling secondary component carriers.

In the second case, g_(PCC)(i) for the SC format is only updated withpower control parameter from PCC downlink control message 70. Meanwhile,g_(SCC)(i) for the CA format is only updated based on power controlparameters in downlink control messages 70 scheduling secondarycomponent carriers. In various embodiments, both g_(PCC)(i) andg_(SCC)(i) may be updated as soon as a corresponding power controlparameter is received or may only be updated if the corresponding formatfor uplink control messages 72 is also used (i.e., g_(PCC)(i)) is onlyupdated if the SC format is used and g_(SCC)(i) is only updated if theCA format is used).

After determining the appropriate transmission power level, wirelessterminal 20 then transmits an uplink control message 72 for the subframeto base station 32 in accordance with a selected format and using thecalculated transmission power level. By using the described techniquesto communicate the appropriate transmission power level for the relevantuplink control message 72, mobile communication system 10 can, inparticular embodiments, facilitate the use of different transmissionpower levels for different control message formats but, at the sametime, minimize the impact that transmission errors in communicatingdownlink control messages 70 have on the selection of appropriatetransmission power levels.

Dynamic Decoding of Uplink Control Messages

As noted above, particular embodiments of mobile communication system 10utilize dynamic decoding of feedback bits in uplink control messages 72to improve decoding performance. More specifically, particularembodiments utilize knowledge of the scheduled component carriers forwireless terminal 20 to improve link reliability and/or reduce thetransmission power requirements for uplink control messages 72.

As part of this dynamic decoding scheme, base station 32 receives uplinkcontrol messages 72 from wireless terminal 20 that have been encoded fortransmission over the radio link between wireless terminal 20 and basestation 32. The following description assumes, for purposes ofillustration, that wireless terminal 20 encodes feedback information inuplink control messages 72 using a (32, O) Reed Muller encoding scheme,where O is the number of feedback bits. Nonetheless, wireless terminal20 may use any suitable encoding scheme with appropriate modification ofthe described decoding techniques. Additionally, the followingdescription assumes, for purposes of illustration, that two feedbackbits are transmitted for each component carrier on which a terminal isscheduled. In alternative embodiments, the number of bits in thefeedback information may vary depending on, for example, whether spatialbundling is employed or whether certain component carriers areconfigured to only be used for single-codeword transmissions.

Thus, in particular embodiments, wireless terminal 20 encodes thefeedback bits using the (32, O) block code. In particular embodiments,the code words of this block code are a linear combination of the eleven(11) basis sequences denoted M_(i,n) and defined in Table 5.2.2.6.4-1 of3GPP TS 36.212, “Multiplexing and channel coding,” V 9.0.0, which isincorporated herein by reference in its entirety. The encoded block isdenoted by b₀, b₁, b₂, b₃, . . . , b_(B-1) where B=32 and:

$\begin{matrix}{b_{i} = {\sum\limits_{n = 0}^{O - 1}\; {\left( {o_{n} \cdot M_{i,n}} \right){mod}\mspace{14mu} 2}}} & {{Equation}\mspace{14mu} (2)}\end{matrix}$

where i=0, 1, 2, . . . , B−1.

The encoded block may then be processed as appropriate for the relevantconfiguration of mobile communication system 10 before being transmittedby wireless terminal 20. For instance, in certain LTE embodiments, ratematching is performed on the encoded bits to generate a 48-bit encodedsequence for transmission as part of a Discrete Fourier Transform SpreadOrthogonal Frequency Division Multiplexed (DFTS-OFDM) based PUCCH. Theencoded bit sequence is then scrambled with cell-specific and/orsymbol-dependent sequences. Two 24 bit groups are each assigned to aseparate slot and converted into twelve quadrature phase-shift keying(QPSK) symbols, DFT precoded, spread across five DFTS-OFDM symbols, andtransmitted within one resource block (bandwidth) and five DFTS-OFDMsymbols (time).

Base station 32 receives the encoded feedback information as part of anuplink control message 72. Base station 32 then decodes the encodedfeedback information using knowledge of scheduling informationassociated with wireless terminal 20 to facilitate decoding. Toillustrate, consider an example in which base station 32 has scheduledtwo component carriers (Component Carrier 3 and Component Carrier 4) outof five configured component carriers for transmissions to wirelessterminal 20 during a particular subframe and in which wireless terminal20 uses two feedback bits to report on each configured componentcarrier. Since the codebook used in this example would be configured tosupport ten feedback bits, wireless terminal 20 will use ten Reed Mullerbases with indices {0, 1, 2, 3, 4, 5, 6, 7, 8, 9} to encode the fiveconfigured component carriers in this case. That is, a nominal (48, 10)channel code is used by wireless terminal 20.

Because, in this example, base station 32 has not sent any assignmentsor scheduling grants relating to Component Carrier 0, Component Carrier1, or Component Carrier 2, the ten-bit sequence of feedback bits shouldstart with six zeros. Therefore base station 32 using its knowledge ofthis scheduling information can decode an effective (48, 4) channel codeusing only the Reed Muller bases with indices {6, 7, 8, 9}. For thisexample, this knowledge effectively reduces the number of possiblecodewords to search from 1024 to only 16. As a result, the requiredoperating signal-to-noise ratio (SNR) can be reduced, and thetransmission power used by wireless terminal 20 in transmitting feedbackinformation can likewise be reduced. For instance, in the case of fiveconfigured component carriers, dynamic decoding can reduce the necessarytransmission power increase on wireless terminal 20 when transmitting CAformat uplink control messages 72 from 4 dB down to no increase in mostcases and a small increase in a minority of cases. The required smalltransmission power increase for the minority cases can be added to powercontrol parameters in downlink control messages 70 scheduling secondarycomponent carriers to inform wireless terminal 20.

Therefore, in particular embodiments of mobile communication system 10,base station 32 utilizes an improved maximum likelihood decoding schemeto decode the first order Reed-Muller-code encoded feedback informationin uplink control messages 72 based on knowledge of the schedulinginformation that prompted the feedback information. In particularembodiments of mobile communication system 10, this decoding schemecomprises a first decoding algorithm used for uplink control messages 72that include up to six feedback bits and a second decoding algorithmused for uplink control messages 72 that include more than six feedbackbits.

More specifically, the first decoding algorithm provides an efficienttechnique for dynamic decoding of CA format uplink control messages 72supporting up to six feedback bits (i.e., O≦6). As noted above, inparticular embodiments, wireless terminal 20 uses an LTE (32, O) blockcode related to the first order (32, 6) Reed-Muller code to encodefeedback bits in uplink control messages 72. For example, when wirelessterminal 20 encodes an uplink control message 72 for a cell 60supporting five configured component carriers and employing spatialbundling (i.e., an uplink control message 72 that includes five bits offeedback information), the LTE (32, 5) block code is used for forwarderror correction. A brute-force maximum likelihood (ML) decoding of thiscode would require 32×32=1024 operations. Using the first decodingalgorithm, an efficient decoding can be completed in particularembodiments of mobile communication system 10 in only 32×log₂32=160operations.

In particular embodiments, this first decoding algorithm is implementedby:

-   -   1. Applying the interleaving shown in Equation (3) to the        received soft value sequence, r₀, r₁, r₂, r₃, . . . , r₃₁        corresponding to the LTE (32, O) block code to convert the        received soft value sequence into a received vector, s₀, s₁, s₂,        s₃, . . . , s₃₁, corresponding to the first order (32,6)        Reed-Muller code:

Equation (3) s₀ = r₃₁, s₁ = r₀, s₂ = r₂₀, s₃ = r₁, s₄ = r₂, s₅ = r₂₁, s₆= r₃, s₇ = r₄, s₈ = r₂₂, s₉ = r₅, s₁₀ = r₆, s₁₁ = r₂₃, s₁₂ = r₇, s₁₃ =r₈, s₁₄ = r₉, s₁₅ = r₂₄, s₁₆ = r₁₉ s₁₇ = r₂₅ s₁₈ = r₁₀ s₁₉, = r₁₁ s₂₀ =r₁₂ s₂₁ = r₁₃ s₂₂ = r₂₆, s₂₃ = r₂₇ s₂₄ = r₁₄ s₂₅ = r₁₅ s₂₆ = r₂₈ s₂₇ =r₁₆ s₂₈ = r₁₇ s₂₉ = r₁₈ s₃₀ = r₂₉ s₃₁ = r₃₀

-   -   2. Perform a fast Hadamard transform on the received vector s₀,        s₁, s₂, s₃, . . . , s₃₁ to obtain the transformed values h₀, h₁,        h₂, h₃, . . . , h₃₁    -   3. Find the index and the sign of the transformed value with the        largest absolute value from a subset of the transformed values.        The subset is determined by the set of known information bits.    -   4. Obtain an information bit sequence estimate based on the        index of the best transformed value and its sign.

To illustrate this technique, consider a first example where basestation 32 has scheduled wireless terminal 20 to use all fivecurrently-configured component carriers. In this case, the set of knowninformation bits would be [o₅]=[0], because Component Carrier 5 is notconfigured and thus is not scheduled. Suppose the actual feedback bitsequence generated by wireless terminal 20 is [1, 1, 0, 0 1] for thefive configured component carriers, indicating that wireless terminal 20successfully received scheduled transmissions on Component Carrier 0,Component Carrier 1, and Component Carrier 4. In an embodiment using theexample encoding scheme described above, wireless terminal 20 would thenproduce a corresponding first-order Reed-Muller encoded codeword of [1,0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1, 0, 0,1, 0, 1, 0, 1, 0, 1] and transmit the codeword to base station 32 aspart of an uplink control message 72.

Base station 32 receives the transmitted uplink control message 72 andmay then perform the interleaving described by Equation (3) on the softvalue sequence corresponding to the feedback bits to generate a receivedvector, s₀, s₁, s₂, s₃, . . . , s₃₁. Suppose that, because ofinterference and noise in the wireless communication channel, thereceived vector, s₀, s₁, s₂, s₃, . . . , s₃₁, for this example is givenby [−0.8, 0.5, −0.9, 0.7, −0.8, 1.4, −1.1, 0.1, 1.2, −0.3, 1.4, −1.8,0.9, −1.4, 0.5, −1.5, −0.9, 0.7, −1.0, 0.9, −1.3, 1.1, −0.6, 2.0, 0.4,−1.6, 1.5, −1.2, 0.3, −0.7, 1.7, −0.8]. The resulting Hadamardtransformed values for this example are shown on the left-hand side ofthe following Equation (4):

Eq. (4) Positive Negative h0 = −1.3 -> 000000 or 100000 h1 = 2.3 ->010000 or 110000 h2 = −1.3 -> 001000 or 101000 h3 = −3.8 -> 011000 or111000 h4 = −1.1 -> 000100 or 100100 h5 = 3.6 -> 010100 or 110100 h6 =0.7 -> 001100 or 101100 h7 = −0.0 -> 011100 or 111100 h8 = 1.3 -> 000010or 100010 h9 = −32.0 -> 010010 or 110010 h10 = 0.7 -> 001010 or 101010h11 = 3.6 -> 011010 or 111010 h12 = −2.0 -> 000110 or 100110 h13 = 0.7-> 010110 or 110110 h14 = −0.8 -> 001110 or 101110 h15 = 2.7 -> 011110or 111110 h16 = −2.2 -> 000001 or 100001 h17 = 3.1 -> 010001 or 110001h18 = 7.7 -> 001001 or 101001 h19 = −0.3 -> 011001 or 111001 h20 = 4.8-> 000101 or 100101 h21 = −1.9 -> 010101 or 110101 h22 = −2.1 -> 001101or 101101 h23 = −1.3 -> 011101 or 111101 h24 = −1.1 -> 000011 or 100011h25 = 1.5 -> 010011 or 110011 h26 = −1.4 -> 001011 or 101011 h27 = −2.2-> 011011 or 111011 h28 = −2.0 -> 000111 or 100111 h29 = −0.1 -> 010111or 110111 h30 = −4.2 -> 001111 or 101111 h31 = 4.2 -> 011111 or 111111

In Step 3, the index and the sign of the transformed value with thelargest absolute value from a subset of the transformed values is found.Since the set of known information bit is [o₅]=[0], the search should belimited to h_(b) with bε{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15}, the indices for the candidates corresponding to [o₅]=[0]—thatis, the indices for all candidates having a “0” for the final bit. Forthis example, h₉ has the largest absolute value in that subset and it'ssign is negative. As indicated by the right-hand side of Equation (4),each of the Hadamard transformed values (h_(b)) is associated with a bitsequence. In the example embodiment, each of the transformed values isassociated with a six-bit sequence that comprises a five-bit binaryrepresentation of the index of the relevant transformed value (in thesecond through sixth bits, with the sixth bit being the most significantof the five-bit representation) and an additional bit (the first bit)that corresponds to the sign of the transformed value (with a negativetransformed value mapping to a first bit of “1” and a positivetransformed value mapping to a first bit of “0”). Thus, for this exampleembodiment, h₉ having the greatest magnitude and a positive valuecorresponds to a bit sequence estimate of [1 1 0 0 1 0] for theoriginal, unencoded feedback information. Since base station 32 knowsthat [o₅]=[0] in this example, base station 32 can determine that theestimated feedback bit sequence [1 1 0 0 1 0] corresponds to atransmitted feedback sequence of [1 1 0 0 1]. Thus, base station 32 isable to recover the original feedback information sent by wirelessterminal 20.

Consider a second example where base station 32 schedules ComponentCarrier 0, Component Carrier 1, Component Carrier 2, and ComponentCarrier 4. In this case, the subset of known information bits is[o₃,o₅]=[0,0], based on the fact that Component Carrier 3 has not beenscheduled for wireless terminal 20 and Component Carrier 5 is notconfigured. Therefore, the search subset for Step 3 is limited to h_(b)with bε{0, 1, 2, 3, 8, 9, 10, 11}, the indices for the candidate bitsequences for which [o₃,o₅]=[0,0].

Consider a third example where base station 32 schedules ComponentCarrier 0, Component Carrier 1, and Component Carrier 4. In this case,the subset of known information bits is [o₂,o₃,o₅]=[0,0,0], based on thefact that Component Carrier 2, Component Carrier 3, and ComponentCarrier 5 have not been scheduled. Therefore, the search subset for step3 is limited to h_(b) with bε{0, 1, 8, 9, 11}, the indices for thecandidate bit sequences for which [o₂,o₃,o₅]=[0,0,0].

As noted above, particular embodiments of mobile communication system 10may utilize a second algorithm for decoding feedback bits in uplinkcontrol messages 72 containing more than six feedback bits. Inparticular embodiments, wireless terminal 20 uses an LTE (32, O) blockcode related to the second order (32, 16) Reed-Muller code to encodethis feedback information. For example, in such embodiments, a CA formatuplink control message 72 that provides feedback on five configuredcomponent carriers (without employing spatial bundling) contains tenfeedback bits, and wireless terminal 20 uses the LTE (32,10) block codefor forward error correction encoding. Wireless terminal 20 thentransmits the encoded uplink control message 72 to base station 32.

By utilizing the second algorithm, particular embodiments of basestation 32 may perform decoding of feedback information in such anuplink control message 72 with substantially lower complexity.

According to this second algorithm, base station 32 decodes feedbackbits by:

-   -   1. Applying the interleaving shown in Equation (3) on the        received soft value sequence r₀, r₁, r₂, r₃, . . . , r₃₁        corresponding to the LTE (32, O) block code into a received        vector s₀, s₁, s₂, s₃, . . . , s₃₁ corresponding to the second        order (32,10) Reed-Muller code.    -   2. Forming a set of hypothesized sequences for [o₆,o₇,o₈,o₉].        The hypothesized sequences may represent all possible        combinations of [o₆,o₇,o₈,o₉]. In particular embodiments,        however, base station 32 may use known scheduling information to        eliminate candidates that are not possible.    -   3. For each of the hypothesized sequence for [o₆,o₇,o₈,o₉]:        -   a. Multiplying the received vector s₀, s₁, s₂, s₃, . . . ,            s₃₁ with the covering vector c₀, c₁, c₂, c₃, . . . , c₃₁            corresponding to the hypothesized sequence for [o₆,o₇,o₈,o₉]            in the table of FIG. 4 to obtain a modified received vector            s′₀, s′₁, s′₂, s′₃, . . . , s′₃₁;        -   b. Performing a fast Hadamard transform on the modified            received vector s′₀, s′₁, s′₂ s′₃, . . . , s′₃₁ to obtain            the transformed values h₀, h₁, h₂, h₃, . . . , h₃₁;        -   c. Finding the index and the sign of the transformed value            with the largest absolute value from a subset of the            transformed values. The subset is determined by the set of            known information bits; and        -   d. Obtaining an intermediate information bit sequence            estimate for the second order Reed-Muller code based on the            index of the best transformed value and its sign. The            absolute value of the transformed value associated with the            intermediate information bit sequence estimate is also            retained as the intermediate metric; and    -   4. Obtaining the final information bit sequence estimate from        the intermediate information bit sequence estimate for the        second order Reed-Muller code associated with the best        intermediate metric.

The covering vectors referenced by Step 3(a) above comprise arepresentation of the associated hypothesis sequence that has beenencoded using the same encoding scheme implemented on the transmittingside, possibly with additional processing to facilitate detection of theremaining bits. For example, in the embodiment described by the table inFIG. 4, each hypothesized sequence is associated with a covering vectorc₀, c₁, c₂, c₃, . . . , c₃₁ that represents a version of thehypothesized sequence that has been encoded using Equation (2) and thebasis sequences associated with the bits addressed by the hypothesizedsequence. Thus, for the illustrated example, an example in which thehypothesized sequences address bits o₆, o₇, o₈, and o₉, the coveringvectors represent versions of the hypothesized sequences that have beenencoded using Equation 1 and only the basis sequences M_(i,6), M_(i,7),M_(i,8), and M_(i,9). In other words, each example covering vector isbased on an encoding of the corresponding hypothesized sequence usingEquation (2) for i=6, 7, 8, 9. In the example embodiment described byFIG. 4, the resulting encoded bits (b_(i)) are then additionallyprocessed by interleaving the bits according to Equation (3) andapplying a binary to bipolar mapping, under which “0” values are mappedto “1” and “1” values are mapped to “−1,” to produce the examplecovering vectors shown in the table of FIG. 4.

To illustrate how the second algorithm may be implemented by basestation 32 in particular embodiments, consider an example where basestation 32 has scheduled Component Carrier 0, Component Carrier 1, andComponent Carrier 3. In this case, the set of known information bitswould be [o₄,o₅,o₈,o₉]=[0,0,0,0]. Suppose the actual feedback bitsequence generated by wireless terminal 20 is [1, 1, 0, 1, 0, 1] for thethree scheduled component carriers, indicating that wireless terminal 20successfully received assignments or scheduling grants and thecorresponding scheduled transmissions for both antennas on CC0 and forone antenna on each of CC1 and CC3. The nominal feedback bit sequenceencoded by wireless terminal 20 would then be [1, 1, 0, 1, 0, 0, 0, 1,0, 0]. In an embodiment using the example encoding scheme describedabove, wireless terminal 20 would then produce a correspondingsecond-order Reed-Muller encoded codeword of [1, 0, 1, 0, 0, 1, 0, 0, 0,1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0] andtransmit the codeword to base station 32 as part of an uplink controlmessage 72.

Base station 32 receives the transmitted uplink control message 72 andmay then perform the interleaving described by Equation 2 on the softvalue sequence corresponding to the feedback bits to generate a receivedvector, s₀, s₁, s₂, s₃, . . . , s_(B-1). Suppose the received vector isgiven by s₀, s₁, s₂, s₃, . . . , s_(B-1)=[−1.2, 0.2, −0.9, 1.1, 0.4,−0.4, 1.6, 1.0, 1.2, −0.9, −1.1, 1.4, −1.3, 2.1, 0.9, 1.1, −0.5, −1.0,1.0, 0.6, −0.9, 0.3, 1.4, 1.8, 0.7, −0.6, −0.4, 0.2, 0.3, 1.3, −1.2,1.3] because of interference and noise in the wireless communicationchannel. In this example, [o₈,o₉] is known to be [0,0] as the fifthconfigured component carrier was not scheduled. Thus, only fourhypotheses need to be formed in Step 2 for [o₆,o₇,o₈,o₉]. Moreover,since [o₄,o₅] is known to be [0,0], the search subset for Step 3 islimited to h_(b) with b ε{0, 1, 2, 3, 4, 5, 6, 7}.

For the hypothesis [o₆,o₇,o₈,o₉]=[0,0,0,0], the values of the coveringvector are all “1” (as indicated in the table of FIG. 4). Hence themodified received vector s′₀, s′₁, s′₂, s′₃, . . . , s′₃₁ is identicalto the received vector s₀, s₁, s₂, s₃, . . . , s_(B-1). The relevantHadamard transformed values and their associated bit sequences are:

(4) Positive Negative h0 = 9.4 -> 000000 or 100000 h1 = −9.6 -> 010000or 110000 h2 = −10.0 -> 001000 or 101000 h3 = 4.9 -> 011000 or 111000 h4= −10.1 -> 000100 or 100100 h5 = 4.9 -> 010100 or 110100 h6 = 2.0 ->001100 or 101100 h7 = 9.4 -> 011100 or 111100The intermediate information bit sequence estimate for the second orderReed-Muller code is hence [1, 0, 0, 1, 0, 0, 0, 0, 0, 0] and theintermediate metric is 10.1.

For the hypothesis [o₆,o₇,o₈,o₉ ]=[0,1,0,0], the modified receivedvector s′₀, s′₁, s′₂, s′₃, . . . , s′₃₁ is obtained from the receivedvector s₀, s₁, s₂, s₃, s_(B-1) by flip the signs of the 3, 4, 5, 10, 11,13, 14, 15, 18, 20, 21, 22, 23, 25, 27, 31-th values. The relevantHadamard transformed values and their associated bit sequences are:

Positive Negative h0 = −2.3 -> 000000 or 100000 h1 = 4.5 -> 010000 or110000 h2 = −2.0 -> 001000 or 101000 h3 = −2.8 -> 011000 or 111000 h4 =0.4 -> 000100 or 100100 h5 = −30.0 -> 010100 or 110100 h6 = 0.3 ->001100 or 101100 h7 = 3.8 -> 011100 or 111100The intermediate information bit sequence estimate for the second orderReed-Muller code is hence [1, 1, 0, 1, 0, 0, 0, 1, 0, 0] and theintermediate metric is 30.0.

For the hypothesis [o₆,o₇,o₈,o₉]=[1,0,0,0], the relevant Hadamardtransformed values and associated bit sequences are:

Positive Negative h0 = 8.9 -> 000000 or 100000 h1 = −2.0 -> 010000 or110000 h2 = −4.7 -> 001000 or 101000 h3 = −7.1 -> 011000 or 111000 h4 =4.8 -> 000100 or 100100 h5 = −1.6 -> 010100 or 110100 h6 = 5.7 -> 001100or 101100 h7 = 4.6 -> 011100 or 111100The intermediate information bit sequence estimate for the second orderReed-Muller code is hence [0, 0, 0, 0, 0, 0, 1, 0, 0, 0] and theintermediate metric is 8.9.

For the hypothesis [o₆,o₇,o₈,o₉]=[1,1,0,0], the relevant Hadamardtransformed values and associated bit sequences are:

Positive Negative h0 = 1.1 -> 000000 or 100000 h1 = 6.1 -> 010000 or110000 h2 = −9.9 -> 001000 or 101000 h3 = 0.4 -> 011000 or 111000 h4 =−0.7 -> 000100 or 100100 h5 = −3.4 -> 010100 or 110100 h6 = −10.0 ->001100 or 101100 h7 = −4.2 -> 011100 or 111100The intermediate information bit sequence estimate for the second orderReed-Muller code is hence [1, 0, 1, 1, 0, 0, 1, 1, 0, 0] and theintermediate metric is 10.0.

After cycling through all four hypothesized sequences for [o₆,o₇,o₈,o₉]in this example, base station 32 determines that the best metric is 30.0and the best information bit sequence estimate for the second-orderReed-Muller code is [1, 1, 0, 1, 0, 0, 0, 1, 0, 0]. Discarding from thebit sequence estimates feedback bits corresponding to unscheduledcomponent carriers (i.e., the known bits [o₄,o₅,o₈,o₉]=[0,0,0,0]), basestation 32 produces a final estimate for the feedback bit sequence of[1, 1, 0, 1, 0, 1], which is consistent with the original feedback bitssequence transmitted by wireless terminal 20.

For this example, a brute-force ML decoder would require 32×2⁶=2048operations. Using this second algorithm, particular embodiments of basestation 32 are able to decode the received feedback bits with foursign-flippings and four fast Hadamard transforms for a total complexityof 768 operations. Thus, particular embodiments of base station 32 candecode feedback bits in CA format uplink control messages 72 usingdecoding techniques with substantially reduced complexity. FIG. 5 showsa comparison of the operational complexity of decoding using abrute-force ML decoding technique to that achieved when the decodingtechniques described above are implemented in certain embodiments ofmobile communication system 10.

Thus, particular embodiments of mobile communication system 10 mayemploy control signaling techniques with improved reliability and/ordecreased overhead. Additionally, particular embodiments of mobilecommunication system 10 may reduce the operational complexity ofdecoding certain types of control signaling. As a result, certainembodiments of mobile communication system 10 may provide numerousoperational benefits. Nonetheless, specific embodiments of mobilecommunication system 10 may provide some, none, or all of thesebenefits.

FIG. 6 is a block diagram illustrating in greater detail contents of aparticular embodiment of a wireless terminal 20. As shown in FIG. 6, theillustrated embodiment of wireless terminal 20 includes a processor 602,a memory 604, a transmitter 606, a receiver 608, and an antenna 610.

Processor 602 may represent or include any form of processing component,including dedicated microprocessors, general-purpose computers, or otherdevices capable of processing electronic information. Examples ofprocessor 602 include field-programmable gate arrays (FPGAs),programmable microprocessors, digital signal processors (DSPs),application-specific integrated circuits (ASICs), and any other suitablespecific- or general-purpose processors. Although FIG. 6 illustrates,for the sake of simplicity, an embodiment of wireless terminal 20 thatincludes a single processor 602, wireless terminal 20 may include anynumber of processors 602 configured to interoperate in any appropriatemanner.

Memory 604 stores processor instructions, configuration information,power control parameters, format definitions, and/or any other datautilized by wireless terminal 20 during operation. Memory 604 maycomprise any collection and arrangement of volatile or non-volatile,local or remote devices suitable for storing data, such as random accessmemory (RAM), read only memory (ROM), magnetic storage, optical storage,or any other suitable type of data storage components. Although shown asa single element in FIG. 6 memory 604 may include one or more physicalcomponents local to or remote from wireless terminal 20.

Antenna 610 represents any suitable conductor capable of receiving andtransmitting wireless signals. Transmitter 606 transmits radiofrequency(RF) signals over antenna 610, and receiver 608 receives from antenna610 RF certain signals transmitted by access network 30. Although theexample embodiment in FIG. 6 includes certain numbers and configurationsof antennas, receivers, and transmitters, alternative embodiments ofwireless terminal 20 may include any suitable number of thesecomponents. Additionally, transmitter 606, receiver 608, and/or antenna610 may represent, in part or in whole, the same physical components.For example, particular embodiments of wireless terminal 20 include atransceiver representing both transmitter 606 and receiver 608.

FIG. 7 is a flowchart illustrating example operation of a particularembodiment of wireless terminal 20 in selecting a format for an uplinkcontrol message 72 to use in responding to scheduled transmissionstransmitted by access network 30. The steps illustrated in FIG. 7 may becombined, modified, or deleted where appropriate. Additional steps mayalso be added to the example operation. Furthermore, the described stepsmay be performed in any suitable order.

In particular embodiments, wireless terminal 20 may be informed of thecomponent carriers configured for within the cell 60 served by basestation 32. Thus, in FIG. 7, operation begins with wireless terminal 20receiving, at step 700, configuration information. This configurationinformation identifies the primary carrier configured for cell 60 andany secondary component carriers configured for cell 60. At step 702,wireless terminal 20 stores this configuration information for lateruse.

In this example, base station 32 transmits to wireless terminal 20 oneor more downlink control messages 70 scheduling component carriers foruse by wireless terminal 20. As explained above with respect to FIG. 2,this scheduled use may involve receiving signals from base station 32 onthe relevant component carrier or transmitting signals to base station32 on the relevant component carrier. Base station 32 transmits at leastPCC downlink control message 70 a scheduling wireless terminal 20 toreceive a downlink transmission on the primary component carrier. Basestation 32 may also transmit one or more SCC downlink control messages70 b-d scheduling wireless terminal to receive a downlink transmissionon secondary component carriers.

At step 704, wireless terminal 20 begins receiving downlink controlmessages 70 from base station 32. At step 706, wireless terminal 20determines whether any of the successfully received downlink controlmessages 70 include scheduling information scheduling wireless terminal20 to receive a transmission on a secondary component carrier. Inparticular embodiments, wireless terminal 20 may use storedconfiguration information to determine whether the schedulinginformation of each of the various received downlink control messages 70is scheduling wireless terminal 20 on the primary component carrier or asecondary component carrier. Based on this determination, wirelessterminal 20 then selects a format for an uplink control message 72. Inparticular embodiments, wireless terminal 20 selects from between afirst format (e.g., the CA format described above) that carries separatefeedback information for each of the configured component carriers and asecond format (e.g., the SC format described above) that carriesfeedback information for the primary component carrier in cell 60, butdoes not include separate feedback bits for any of the secondarycomponent carriers.

For example, in particular embodiments, wireless terminal 20 selects thesecond format (as shown at step 708) if wireless terminal 20 has onlyreceived a downlink control message 70 scheduling wireless terminal 20to receive a transmission on the primary component carrier. The secondformat only includes feedback bits for a single component carrier(specifically, the primary component carrier). However, if wirelessterminal 20 has received any downlink control messages 70 schedulingwireless terminal 20 to receive a transmission on a secondary carrierduring the corresponding subframe, then wireless terminal 20 selects thefirst format instead (as shown at step 710). This first format permitswireless terminal to provide feedback bits for more than one componentcarrier.

After sending the one or more downlink control messages 70 containingthe scheduling information, base station 32 transmits the scheduledtransmissions on the designated component carriers. At an appropriatepoint in time after wireless terminal 20 was scheduled to receive thesetransmissions, wireless terminal 20 provides base station 32 feedbackinformation indicating whether the scheduled transmissions weresuccessfully received. Thus, at step 712, wireless terminal 20 generatesan uplink control message 72 based on the selected format. This uplinkcontrol message 72 includes feedback information (e.g., one or more HARQfeedback bits) associated with at least one component carrier. As notedabove, this feedback information indicates whether wireless terminal 20successfully received transmissions on the relevant component carrier(s)that were scheduled by any downlink control messages 70 successfullyreceived by wireless terminal 20. If wireless terminal 20 selected thefirst format, the generated uplink control message 72 may includeseparate feedback information for every component carrier configured forcell 60.

At step 714, wireless terminal 20 transmits the generated uplink controlmessage 72 to base station 32. In particular embodiments, when basestation 32 schedules wireless terminal 20 to receive transmissions onsecondary component carriers in addition to the primary componentcarrier but only receives an uplink control message 72 with feedbackinformation for a single component carrier, base station 32 isconfigured to recognize that the component carrier associated with thefeedback information is the primary component carrier and that wirelessterminal 20 must not have received any of the control messages 70scheduling secondary carriers that base station 32 transmitted duringthe subframe. Thus, in particular embodiments, base station 32 cancorrectly interpret the feedback information in the uplink controlmessage 72 despite the fact that the received downlink control message70 may not include explicit feedback information for every componentcarrier on which base station 32 scheduled wireless terminal 20 toreceive a transmission. The operation of wireless terminal 20 may thencontinue indefinitely or end as shown in FIG. 7.

FIG. 8 is a flowchart illustrating example operation of a particularembodiment of wireless terminal 20 in determining a transmission powerlevel to use in transmitting an uplink control message 72 in response toscheduling information transmitted by access network 30. The stepsillustrated in FIG. 8 may be combined, modified, or deleted whereappropriate. Additional steps may also be added to the exampleoperation. Furthermore, the described steps may be performed in anysuitable order.

As explained above with respect to FIG. 2, wireless terminal 20 may, inparticular embodiments, be informed of the component carriers configuredfor use within cell 60. Accordingly, in FIG. 8, operation begins withwireless terminal 20 receiving, at step 800, configuration informationthat identifies the primary carrier configured for cell 60 and anysecondary component carriers configured for cell 60. At step 802,wireless terminal 20 may store this configuration information for lateruse.

In this example, base station 32 transmits to wireless terminal 20 oneor more downlink control messages 70 scheduling wireless terminal 20 toreceive downlink transmissions on component carriers. Base station 32transmits at least a PCC control message 70 a scheduling wirelessterminal 20 to receive a transmission on the primary component carrierthat contains a first power control parameter. Base station 32 may alsotransmit one or more SCC control messages 70 b-d scheduling wirelessterminal 20 to receive transmissions on secondary component carriers.These SCC downlink control messages 70 b-d each contain power controlparameters as well, either a second power control parameter or one ofmultiple additional power control parameters.

At step 804, wireless terminal 20 begins receiving downlink controlmessages 70 from base station 32. At step 806, wireless terminal 20determines whether any of the successfully received downlink controlmessages 70 include scheduling information scheduling the wirelessterminal to receive a transmission on a secondary component carrier. Ifwireless terminal 20 determines at step 806 that any of the successfullyreceived downlink control messages 70 includes scheduling informationscheduling wireless terminal 20 to receive a transmission on a secondarycomponent carrier, then operation will proceed to step 810. Otherwise,at step 808, wireless terminal 20 will determine a transmission powerlevel based on the first power control parameter included in PCC controlmessage 70 a (assuming the wireless terminal 20 successfully receivesPCC control message 70 a).

However, if wireless terminal 20 determines at step 806 that wirelessterminal 20 has successfully received at least one downlink controlmessage 70 scheduling wireless terminal 20 to receive a transmission ona secondary component carrier (i.e., one of SCC control messages 70b-d), wireless terminal 20 determines a transmission power level basedon one or more of the power control parameters included in thesuccessfully received SCC control messages 70 b-d. In particularembodiments, wireless terminal 20 may disregard the power controlparameter included in PCC control message 70 a, as shown at step 810.Instead, wireless terminal 20 determines, at step 812, the transmissionpower level based on the second/additional power control parameters inthe successfully received SCC control messages 70 b-d. As explainedabove, wireless terminal 20 may determine the transmission power levelby extracting a common power control parameter included in all of SCCcontrol messages 70 b-d, summing a plurality of different power controlparameters included in the received SCC control messages 70 b-d, orcombining power control parameters from multiple received SCC controlmessages 70 b-d in any appropriate manner.

At step 814, wireless terminal 20 generates an uplink control message 72responding to downlink control messages 70. The generated uplink controlmessage 72 includes feedback information (e.g., HARQ feedback bits)associated with at least one component carrier. This feedbackinformation indicates whether wireless terminal 20 has received ascheduled transmission on the associated carrier. As explained withrespect to FIG. 7, particular embodiments of wireless terminal 20 maychoose a format for this uplink control message 72 based on whether ornot wireless terminal 20 successfully received any of SCC controlmessages 70 b-d. At step 816, wireless terminal 20 transmits thegenerated uplink control message 72 to base station 32 at the determinedtransmission power level. Operation of wireless terminal 20 may thencontinue indefinitely or end as shown in FIG. 8.

FIG. 9 is a block diagram illustrating in greater detail the contents ofa particular embodiment of a network node 900 managing the transmissionpower of wireless terminal 20 in transmitting uplink control messages 72and/or of decoding uplink control messages 72 transmitted by wirelessterminal 20. Network node 900 may represent any suitable element ofaccess network 30 capable of providing the described functionality, suchas base station 32 in the embodiment illustrated by FIG. 1. As shown inFIG. 9, the example embodiment of network node 900 includes a nodeprocessor 902, a node memory 904, and a communication interface 906.

Node processor 902 may represent or include any form of processingcomponent, including dedicated microprocessors, general-purposecomputers, or other forms of electronic circuitry capable of processingelectronic information. Examples of node processor 902 includefield-programmable gate arrays (FPGAs), programmable microprocessors,digital signal processors (DSPs), application-specific integratedcircuits (ASICs), and any other suitable specific- or general-purposeprocessors. Although FIG. 9 illustrates, for the sake of simplicity, anembodiment of network node 900 that includes a single node processor902, network node 900 may include any number of node processors 902configured to interoperate in any appropriate manner.

Node memory 904 stores processor instructions, carrier configurations,power parameters, and/or any other data utilized by network node 900during operation. Node memory 904 may comprise any collection andarrangement of volatile or non-volatile, local or remote devicessuitable for storing data, such as random access memory (RAM), read onlymemory (ROM), magnetic storage, optical storage, or any other suitabletype of data storage components. Although shown as a single element inFIG. 9, node memory 904 may include one or more physical componentslocal to or remote from network node 900.

Communication interface 906 comprises electronic circuitry and othercomponents suitable to permit network node 900 to communicate withwireless terminal 20. For example, in embodiments in which network node900 represents a node separate from the radio elements of access network30 (e.g., a radio network controller) communication interface 906 mayrepresent circuitry capable of communicating over a wireline connectionbetween network node 900 and the radio elements of access network 30. Insuch embodiments, network node 400 may use communication interface 906to transmit information to radio elements (such as base stations 32)that are capable of communicating wirelessly with wireless terminal 20.As an alternative example, in embodiments in which network node 900itself represents a radio element (such as an enhanced Node B (eNodeB)in a Long Term Evolution (LTE) system), communication interface 906 mayinstead include circuitry and components capable of communicating withwireless terminal 20 over a radio link, such as an antenna andradiofrequency transmitter and receiver.

FIG. 10 is a flowchart illustrating example operation of a particularembodiment of network node 900 in managing the transmission power ofwireless terminal 20 in transmitting uplink control messages 72. Thesteps illustrated in FIG. 10 may be combined, modified, or deleted whereappropriate. Additional steps may also be added to the exampleoperation. Furthermore, the described steps may be performed in anysuitable order.

Operation begins in this example with network node 900 scheduling awireless terminal to receive downlink transmissions on componentcarriers in cell 60 during a particular subframe at step 1000. Forpurposes of this example it is assumed that, during the relevantsubframe, network node 900 schedules wireless terminal 20 to receivetransmissions on the primary component carrier and at least one of thesecondary carriers configured for cell 60.

In order to manage the amount of power wireless terminal 20 will use inconfirming receipt of the downlink control messages 70, network node 900may determine, at step 1002, a first power control parameter forwireless terminal 20 to use in transmitting uplink control messages inaccordance with a first format that permits wireless terminal 20 tocommunicate feedback information relating to only a single componentcarrier (in this case, the primary component carrier for cell 60). Oncethe first power control parameter has been generated, network node 900may generate, at step 1004, PCC control message 70 a that includes thefirst power control parameter and scheduling information schedulingwireless terminal 20 a transmission on the primary component carrierduring the subframe.

Because in this example network node 900 has scheduled wireless terminal20 to receive a transmission on at least one secondary component carrierin addition to the primary component carrier, network node 900 alsodetermines one or more additional power control parameters for thewireless terminal to use in transmitting an uplink control message 72 inaccordance with a second format at step 1006. This second uplink controlmessage format permits wireless terminal 20 to communicate feedbackinformation relating to multiple component carriers.

As noted above, base station 32 may determine the one or more additionalpower control parameters in any appropriate manner depending on theconfiguration and capabilities of base station 32. For example, inparticular embodiments, base station 32 may determine a single powercontrol parameter for use by wireless terminal 20 in responding to SCCcontrol messages 70 b-d scheduling transmissions on secondary componentcarriers and may include this same power control parameter in all SCCcontrol messages 70 b-d. Base station 32 may determine this single powercontrol parameter based on the number of component carriers configuredfor cell 60, based on the number of component carriers scheduled forwireless terminal in this subframe, based on the specific componentcarriers scheduled or configured (e.g., using a lookup table similar tothose in FIGS. 3A-3D), and/or based on any other appropriate factor orconsideration. In alternative embodiments, base station 32 may determinemultiple different power control parameters, one for each secondarycomponent carrier on which wireless terminal 20 is scheduled to receivea transmission during the subframe. In general, base station 32 may useany suitable technique to determine the one or more additional powercontrol parameters.

After determining the additional power control parameter(s), basestation 32 generates one or more SCC control messages (e.g., SCC controlmessages 70 b-d) at step 1008, one for each of the secondary componentcarriers on which base station 32 has scheduled wireless terminal 20 toreceived transmissions during the relevant subframe. The SCC controlmessage(s) each include the additional power control parameter or, ifmultiple are generated, one of the additional power control parameters.Base station 32 then transmits PCC control message 70 a and SCC controlmessages 70 b-d to wireless terminal 20 at step 1010. Operation of basestation 32 with respect to transmitting downlink control messages 70 maythen terminate as shown in FIG. 10.

FIGS. 11 and 12 are flowcharts illustrating example operation of aparticular embodiment of network node 900 in decoding informationtransmitted by wireless terminal 20. In particular, FIG. 11 illustratesan example in which network node 900 implements the first algorithmdescribed above on an uplink control message 72 carrying six or fewerfeedback bits, and FIG. 12 illustrates an example in which network node900 implements the second algorithm described above on an uplink controlmessage 72 carrying more than six feedback bits. Certain embodiments ofnetwork node 900 may be capable of implementing only one of thealgorithms, while other embodiments may be capable of implementing both.In particular embodiments, network node 900 may be configured to selectan appropriate algorithm to use based on the number of componentcarriers currently configured for use in cell 60. The steps illustratedin FIGS. 11 and 12 may be combined, modified, or deleted whereappropriate. Additional steps may also be added to the exampleoperation. Furthermore, the described steps may be performed in anysuitable order.

In FIG. 11, operation begins with network node 900 transmitting one ormore downlink control messages 70 to wireless terminal 20 at step 1100.The downlink control messages 70 include scheduling informationscheduling wireless terminal 20 to receive transmissions on a pluralityof component carriers configured for cell 60. Wireless terminal 20receives the transmitted downlink control messages 70 and attempts todecode them. Because network node 900 and wireless terminal 20communicate over an imperfect channel, network node 900 may not receivesome of the transmitted downlink control messages 70 at all or may beunable to decode some of these downlink control messages 70 because ofcorruption occurring during transmission. As a result, wireless terminal20 will respond to downlink control messages 70 by generating feedbackinformation (e.g., HARQ feedback bits in embodiments implementing LTE)indicating the component carriers for which wireless terminal 20successfully received scheduled transmissions.

Wireless terminal 20 then encodes the unencoded feedback information.For the example in FIG. 11, it is assumed that the feedback informationincludes six or less bits and that wireless terminal 20 encodes thefeedback information using a first-order Reed Muller code. Afterencoding the feedback information, wireless terminal 20 transmits theencoded feedback information to network node 900 as part of an uplinkcontrol message 72 (e.g., as part of a UCI message on the PUCCH inembodiments implementing LTE).

Network node 900 receives the transmitted uplink control message 72,which includes a vector of encoded information bits as shown at step1102. This vector of encoded information bits comprises an encodedrepresentation of the feedback information bits generated by wirelessterminal 20, but the signal strength of the encoded bits may potentiallyhave been deteriorated as a result of transmission over the radiochannel between wireless terminal 20 and network node 900. As a result,network node 900 attempts to decode the encoded feedback information andto determine the original unencoded feedback information. As part ofthis process, network node 900 generates a vector of transform values byperforming a Hadamard Transform on the received vector at step 1104.

Because network node 900 has the benefit of knowing which componentcarriers network node 900 scheduled wireless terminal 20 on for thecurrent subframe, network node 900 can use this information to eliminatecertain possibilities for the bit combinations transmitted by wirelessterminal 20. Thus, at step 1106, network node 900 identifies a subset ofthe transform values based on scheduling information associated with thewireless terminal 20. Each transform value reflects the likelihood thata feedback information bit sequence associated with that transform valuewas the original, unencoded information bit sequence generated bywireless terminal 20. By limiting analysis of transform values to onlythose transform values associated with realistic candidates, particularembodiments of network node 900 can significantly reduce the processingresources used to determine the best estimate of the original feedbackinformation.

For example, in particular embodiments, network node 900 may store thescheduling information included in the various downlink control messages70 transmitted to wireless terminal 20. This scheduling information mayinclude an indication of the component carriers on which wirelessterminal 20 is scheduled to receive transmissions, informationindicating whether wireless terminal is permitted to transmit schedulingrequests during this subframe, and/or any other appropriate informationpertaining to the transmission resources wireless terminal 20 ispermitted to use during the subframe or the manner in which wirelessterminal 20 is permitted to use such resources. Upon receiving theencoded feedback information, network node 900 uses the storedscheduling information to determine on which component carriers networknode 900 did not schedule wireless terminal 20 to receive a transmissionduring the relevant subframe. Because network node 900 does not transmitany scheduling information to wireless terminal 20 for componentcarriers on which network node 900 did not schedule wireless terminal 20to receive a transmission, network node 900 can safely assume inparticular embodiments that the original feedback information generatedby wireless terminal 20 did not indicate receipt of schedulinginformation for any such component carriers. Based on this assumption,network node 900 can form the subset by eliminating possible candidatesfor the original, unencoded feedback information that would indicatewireless terminal 20 did receive scheduling information for unscheduledcomponent carriers.

At step 1108, network node 900 selects, from the subset of transformvalues, one of the transform values based on a magnitude of the selectedtransform value. Accordingly, network node 900 may then determine anestimate of the original, unencoded feedback information based on a bitsequence associated with the selected transform value at step 1110. Forexample, in particular embodiments, each transformed value in the vectorof transform values is associated with two potential candidates for theoriginal, unencoded feedback information, and network node 900 selectsone of those candidates based on a sign (i.e., positive or negative) ofthe transformed value.

After decoding the original information bits, network node 900 may takeappropriate actions based on the decoded information. For instance, ifthe decoded information indicates that wireless terminal 20 did notsuccessfully receive a transmission scheduled for certain componentcarriers that network node 900 scheduled for wireless terminal 20,network node 900 may, depending on the circumstances, decide tore-schedule some or all of the downlink transmissions. The relevantdownlink transmissions may be selected based, in some manner, on thedecoded feedback bits. Once network node 900 has completed decoding theoriginal information bits, operation of network node 900 may end asindicated in FIG. 11.

FIG. 12 illustrates example operation of an embodiment of network node900 in which network node 900 applies a second algorithm to decode thereceived feedback information. When the original, unencoded feedbackinformation includes more than six bits, it may be more efficient fornetwork node 900 to apply a similar technique to that described abovefor six bits of the encoded feedback information but to test hypothesesfor the remaining bits. As a result, FIG. 12 illustrates an exampleoperation for an embodiment of network node 900 configured to do this.

Operation in this example begins at step 1200 with network node 900transmitting one or more downlink control messages 70 to wirelessterminal 20. Operation proceeds in a similar manner to that describedabove with network node 900 receiving an uplink control message 72transmitted by wireless terminal 20 that contains a vector of encodedinformation bits at step 1202.

At step 1204, network node 900 determines a plurality of hypothesizedsequences corresponding to a first group of the unencoded feedback bits.In particular embodiments, the number of unencoded feedback bits in thisfirst group is equal to the amount by which the original information bitsequence exceeds six bits. For example, if the original, unencodedfeedback information included ten bits, network node 900 would determineevery possible combination for the remaining bits—that is, everypossible 4-bit sequence. However, if network node 900 knows that certaincombinations are not possible based on the scheduling informationoriginally transmitted to wireless terminal 20, network node 900 may beable to eliminate certain sequences. For example, if network node 900did not schedule component carriers associated with the final two bitsof the ten bits of feedback information, network node 900 may be able toeliminate the 4-bit sequences that do not have zeros (or thepredetermined value indicating non-receipt) for the relevant bits aspossible candidates.

After determining the possible hypothesized sequences for the bits inthe first group, network node 900 multiplies the received vector by acovering vector associated with each possible hypothesized sequence togenerate a modified received vector for each hypothesized sequence (ofbits in the first group) at step 1206. At step 1208, network node 900performs a Hadamard Transform on each of the modified received vectorsto obtain a transformed vector associated with each possiblehypothesized sequence (of bits in the first group). Additionally, eachof the transform values is associated with one or more bit sequenceestimates for the second group of bits in the unencoded feedbackinformation. This second group includes the bit of the unencodedfeedback information that are not included in the first group (forpurposes of this example, the second group includes the first six bitsof the unencoded feedback information).

Network node 900 then identifies a subset of the transform values in allof the transform vectors based on the known scheduling information forwireless terminal 20 at step 1210. In particular embodiments, networknode 900 may form the subgroup of transformed values by eliminatingthose transformed values associated with estimates (of the second groupof original information bits) that would indicate wireless terminalreceived scheduling information for component carriers on which networknode 900 did not schedule wireless terminal 20 to receive atransmission. For example, if the second group of bits includedinformation about Component Carrier 0, Component Carrier 1, andComponent Carrier 2, and network node 900 did not schedule wirelessterminal 20 to receive any transmissions on Component Carrier 1 thissubframe, network node 900 would identify the subgroup by eliminatingfrom consideration all transform values associated with estimates forthe second group of bits that would indicate that wireless terminal 20received scheduling information for Component Carrier 1.

Network node 900 then selects from the identified subset of transformvalues a transform value based on a magnitude of the selected transformvalue at step 1212. For example, in particular embodiments, eachtransform value reflects the likelihood that one of the associated bitsequence estimates correctly identifies the second group of bits in theoriginal feedback information. In such embodiments, network node 900selects, from the identified subset of transform values, the transformvalue with the greatest magnitude. Network node 900 may do this bydirectly identifying the transform value with the overall greatestmagnitude. Alternatively, network node 900 may do this iteratively byidentifying intermediate “best” values representing the transform valuewith the greatest magnitude for each transform vector and then selectingthe greatest from among the intermediate values for each transformvector.

At step 1214, network node 900 determines an estimate of the unencodedfeedback information. In particular embodiments, this estimate is formedfrom an estimate of the first group of unencoded feedback bits and anestimate of the second group of unencoded feedback bits. The estimate ofthe first group of unencoded feedback bits is determined based on thehypothesized sequence associated with the modified vector that was usedto generate the selected transform value. The estimate of the secondgroup of unencoded feedback information is a selected one of the bitsequence estimates associated with the selected transform value. Forexample, in particular embodiments, each transform value is associatedwith two bit sequence estimates for the second group and network node900 selects one of the two bit sequence estimates based on a sign of theselected transform value.

After completing the decoding, network node 900 may take appropriateactions based on the decoded information. For example, depending on thecircumstances, network node 900 may decide to retransmit certaindownlink control messages 70 selected in some manner based on thedecoded information. Operation of network node 900 may end with respectto decoding the received information as indicated in FIG. 12.

Although the present invention has been described with severalembodiments, a myriad of changes, variations, alterations,transformations, and modifications may be suggested to one skilled inthe art, and it is intended that the present invention encompass suchchanges, variations, alterations, transformations, and modifications asfall within the scope of the appended claims.

What is claimed is:
 1. A method of decoding encoded informationcommunicated over a radio channel, comprising: receiving a vector ofencoded information transmitted by a wireless terminal, wherein theencoded information comprises an encoded representation of unencodedinformation bits that have been encoded by a second order Reed-Mullercode; determining a plurality of hypothesized sequences corresponding toa first group of the unencoded information bits, wherein eachhypothesized sequence includes an estimate for each of the first groupof unencoded information bits; for each hypothesized sequence,multiplying the received vector by a covering vector associated with therespective hypothesized sequence to obtain a modified received vector;for each modified received vector, generating a vector of transformvalues by performing a Hadamard Transform on the modified receivedvector, wherein each of the transform values is associated with one ormore estimates of a second group of the unencoded information bits;identifying a subset of the transform values based on the schedulinginformation associated with the wireless terminal; selecting, from theidentified subset of transform values, one of the transform values basedon a magnitude of the selected transform value; and determining anestimate of the unencoded information bits, wherein the estimatecomprises: an estimate of the first group of unencoded information bitsbased on the hypothesized sequence associated with the modified vectorused to generate the selected transform value; and an estimate of thesecond group of unencoded information bits associated with the selectedtransform value.
 2. The method of claim 1, wherein determining anestimate of the unencoded information bits transmitted by the wirelessterminal comprises selecting one of two estimates of the second group ofunencoded information bits that is associated with the selectedtransform value based on a sign of the selected transform value.
 3. Themethod of claim 1, wherein: the scheduling information comprisesinformation indicating which of a plurality of carriers the wirelessterminal is scheduled to use; and identifying a subset of the transformvalues based on the scheduling information comprises eliminatingtransform values from the subset based on the carriers the wirelessterminal is scheduled to use.
 4. The method of claim 1, wherein: thescheduling information comprises information indicating whether thewireless terminal is permitted to transmit a scheduling request duringthis subframe; and identifying a subset of the transform values based onthe scheduling information comprises eliminating transform values fromthe subset based on whether the wireless terminal is permitted totransmit a scheduling request during this subframe.
 5. The method ofclaim 1, wherein receiving the vector of encoded information transmittedby the wireless terminal comprises: transmitting a plurality of downlinkcontrol messages to the wireless terminal, each downlink control messageindicating a carrier on which the wireless terminal is scheduled; andreceiving, from the wireless terminal, a vector of encoded informationthat indicates the carriers for which the wireless terminal successfullyreceived a downlink control message.
 6. The method of claim 1, whereinthe unencoded information bits comprise seven or more bits.
 7. A networknode for decoding encoded information communicated over a radio channel,comprising a receiver operable to receive a vector of encodedinformation transmitted by a wireless terminal, wherein the encodedinformation comprises an encoded representation of unencoded informationbits that have been encoded by a second order Reed-Muller code; and aprocessor operable to: determine a plurality of hypothesized sequencescorresponding to a first group of the unencoded information bits,wherein each hypothesized sequence includes an estimate for each of thefirst group of unencoded information bits; for each hypothesizedsequence, multiply the received vector by a covering vector associatedwith the respective hypothesized sequence to obtain a modified receivedvector; for each modified received vector, generate a vector oftransform values by performing a Hadamard Transform on the modifiedreceived vector, wherein each of the transform values is associated withone or more estimates of a second group of the unencoded informationbits; identify a subset of the transform values based on the schedulinginformation associated with the wireless terminal; select, from theidentified subset of transform values, one of the transform values basedon a magnitude of the selected transform value; and determine anestimate of the unencoded information bits, wherein the estimatecomprises: an estimate of the first group of unencoded information bitsbased on the hypothesized sequence associated with the modified vectorused to generate the selected transform value; and an estimate of thesecond group of unencoded information bits associated with the selectedtransform value.
 8. The node of claim 7, wherein the processor isoperable to determine an estimate of the unencoded information bitstransmitted by the wireless terminal by selecting one of two estimatesof the second group of unencoded information bits that is associatedwith the selected transform value based on a sign of the selectedtransform value.
 9. The node of claim 7, wherein: the schedulinginformation comprises information indicating which of a plurality ofcarriers the wireless terminal is scheduled to use; and the processor isoperable to identify a subset of the transform values based on thescheduling information by eliminating transform values from the subsetbased on the carriers the wireless terminal is scheduled to use.
 10. Thenode of claim 7, wherein: the scheduling information comprisesinformation indicating whether the wireless terminal is permitted totransmit a scheduling request during this subframe; and the processor isoperable to identify a subset of the transform values based on thescheduling information by eliminating transform values from the subsetbased on whether the wireless terminal is permitted to transmit ascheduling request during this subframe.
 11. The node of claim 7,further comprising a transmitter operable to transmit a plurality ofdownlink control messages to the wireless terminal, each downlinkcontrol message indicating a carrier on which the wireless terminal isscheduled; and wherein the receiver is operable to receive the vector ofencoded information transmitted by the wireless terminal by receiving,from the wireless terminal, a vector of encoded information thatindicates the carriers for which the wireless terminal successfullyreceived a downlink control message.
 12. The node of claim 7, whereinthe unencoded information bits comprise seven or more bits.